Hypodermic syringes are well known to be used to deliver fluids like medication, for example, to patients. A traditional hypodermic syringe typically includes a syringe barrel having opposed proximal and distal ends. A cylindrical chamber wall extends between the ends and defines a fluid-receiving chamber. The proximal end of the traditional syringe barrel is substantially open and receives a plunger in sliding fluid tight engagement. The distal end of the traditional syringe barrel includes a passage communicating with the chamber. A needle cannula is mounted to the distal end of the traditional syringe barrel such that the lumen of the needle cannula communicates with the passage and the chamber of the syringe barrel. Movement of the plunger in the proximal direction draws fluid through the lumen of the needle cannula and into the chamber. Movement of the plunger in a proximal to distal direction urges fluid from the chamber and through the lumen of the needle cannula.
In recent years, considerable effort has been invested in providing for a syringe for medical use that is both safe and easy to dispose and non-reusable. Some of these syringes include a retractable needle safety feature. However, these mechanisms are somewhat complex, difficult to use and can increase manufacturing costs while decreasing efficiency in the manufacturing process. For example, a retractable needle safety syringe of one type requires the user to push the plunger fully into the barrel until engagement is felt and an audible click is heard. The user then opens a safety clip at the distal end of the barrel. The plunger is then fully retracted. This brings the needle back into the syringe barrel. The plunger is then snapped off and inserted into the open barrel, sealing the needle within the syringe for safe disposal.
Another design incorporates a plunger being pushed forward and rotated. An integrally molded spring locks into the needle hub. The plunger rod is then drawn rearward, and then tension in a spring is released to angle the hub and the needle to the side, thereby disarming the syringe.
Yet, another retractable safety syringe comprises, a plunger, a barrel, an elastomeric piston, hub, and a needle. This design allows a used needle to be withdrawn inside the syringe barrel following use and automatically tilts it sideways. There are conforming luer locks on the barrel and needle hub that allow the needle hub to engage and disengage inside the barrel. Dart-shaped cleats on the inner circumference of the hub selectively engage complimentary cleats on the plunger tip. The plunger can be freely moved back and forth until the needle retraction is desired. At that time the plunger is pushed forward into the needle hub and rotated counterclockwise camming the plunger into the hub and locking the two together. The camming action simultaneously compresses an integrally molded spring on the plunger tip. Continued rotation disengages the hub and releases the coupled components to be drawn rearward. The plunger is then retracted until it is stopped by tabs on the barrel that prevent rearward exit. As the needle clears the mouth of the barrel, the compressed spring is released, deflecting the needle to the barrel sidewall. Needle retention is achieved and the needle is blocked by the forward barrel wall allowing the disarmed syringe with the used needle to be safety stored in the barrel before disposal.
Each of these proposed constructions of retractable needle syringes has certain disadvantages. Many of them have complicated working parts and require complicated procedures to activate the safety mechanisms. In addition to these mechanisms being somewhat complex, they also increase manufacturing costs due to their multiple component configuration, and decrease efficiency in the manufacturing process.
Therefore, a need exists in the art which allows safe and easy disposal of a syringe and prevents re-use. The device should allow use of a variety of standard needles for filling purposes.